<template>
  <view>
    <view>
        <view class="scroll-view-container">
          <!-- 左侧的滚动视图区域 -->
          <scroll-view class="left-scroll-view" scroll-y :style="{height: wh + 'px'}">
            <block v-for="(item, index) in cateList" :key="index">
              <view :class="['left-scroll-view-item', index === active ? 'active' : '']"  @click="activeChanged(index)">{{item.cat_name}}</view>
            </block>
          </scroll-view>
          <!-- 右侧的滚动视图区域 -->
          <scroll-view class="right-scroll-view" scroll-y :style="{height: wh + 'px'}" :scroll-top="scrollTop">
            <view class="cate-lv2" v-for="(item2, index2) in cateList2" :key="index2">
              <view class="cate-lv2-title">/ {{item2.cat_name}} /</view>
              <!-- 动态渲染三级分类的列表数据 -->
                  <view class="cate-lv3-list">
                    <!-- 三级分类 Item 项 -->
                    <view class="cate-lv3-item" v-for="(item3, index3) in item2.children" :key="index3" @click="gotoGoodsList(item3)">
                      <!-- 图片 -->
                      <image :src="item3.cat_icon"></image>
                      <!-- 文本 -->
                      <text>{{item3.cat_name}}</text>
                    </view>
                  </view>
            </view>
          </scroll-view>
        </view>
      </view>
  </view>
</template>

<script>
  export default {
    data() {
      return {
        // 窗口的可用高度 = 屏幕高度 - navigationBar高度 - tabBar 高度
        wh: 0,
        cateList: [],
        cateList2: [],
        active: 0,
        scrollTop: 0
      }
    },
    onLoad() {
      this.getCateList()
      // 获取当前系统的信息
      const sysInfo = uni.getSystemInfoSync()
      // 为 wh 窗口可用高度动态赋值
      this.wh = sysInfo.windowHeight
    },
    methods: {
       // 跳转商品详情
       gotoGoodsList(item3) {
        uni.navigateTo({
            url: '/subpkg/goods_list/goods_list?cid=' + item3.cat_id
          }) 
       },
       // 选中项改变的事件处理函数
        activeChanged(index) {
          this.active = index
          this.cateList2=this.cateList[index].children
          this.scrollTop = this.scrollTop === 0 ? 1 : 0
        },
      async getCateList() {
        const { data: res } = await uni.$http.get('/api/public/v1/categories')
        if (res.meta.status !== 200) return uni.$showMsg()
        this.cateList = res.message
        this.cateList2=res.message[0].children
      }
    }
  }
  
</script>

<style lang="scss">
.scroll-view-container {
  display: flex;

  .left-scroll-view {
    width: 120px;

    .left-scroll-view-item {
      line-height: 60px;
      background-color: #f7f7f7;
      text-align: center;
      font-size: 12px;

      // 激活项的样式
      &.active {
        background-color: #ffffff;
        position: relative;

        // 渲染激活项左侧的红色指示边线
        &::before {
          content: ' ';
          display: block;
          width: 3px;
          height: 30px;
          background-color: #c00000;
          position: absolute;
          left: 0;
          top: 50%;
          transform: translateY(-50%);
        }
      }
    }
  }
}
.cate-lv2-title {
  font-size: 12px;
  font-weight: bold;
  text-align: center;
  padding: 15px 0;
}
.cate-lv3-list {
  display: flex;
  flex-wrap: wrap;

  .cate-lv3-item {
    width: 33.33%;
    margin-bottom: 10px;
    display: flex;
    flex-direction: column;
    align-items: center;

    image {
      width: 60px;
      height: 60px;
    }

    text {
      font-size: 12px;
    }
  }
}
</style>
